Any day now, a 'tsunami' of Brood X cicadas is heading for Frederick County

May 15—The woods of Frederick County were quiet on Friday, save for a rustling breeze and a few chirping birds.

But that's going to change soon.

After spending 17 years underground, feeding on tree roots and gathering their strength, trillions of Brood X periodical cicadas are set to emerge in the coming days. They've begun trickling out from their subterranean crypts already, but University of Maryland entomology professor Michael Raupp doesn't expect the "tsunami" to gather steam until next week.

And then?

"The dam will break," Raupp said, "and we'll have cicadas everywhere."

The insects that will soon blanket the tree-covered areas of Frederick County are the teenage children of those who visited back in 2004. They'll burrow out of the ground, shed their skins and climb into the trees for a love-fest that will last just a few weeks, Raupp said.

Once they've reproduced, they'll die. Their offspring will bounce back toward the ground, bury themselves in the soil, and begin the 17-year process all over again.

"It's a very unique natural phenomenon, with all the interesting elements," Raupp said. "There's birth. There's death. There's romance in the treetops."

Periodical cicadas exclusively emerge in eastern North America, and though they're often incorrectly conflated with locusts, experts say they're largely harmless.

But their singing is another matter. In their quest to attract a mate, male cicadas will spend about a month buzzing for all they're worth, vibrating special organs called tymbals. Their collective chorus can reach 100 decibels — louder than a lawnmower, a leaf blower or a motorcycle.

"I'm interested to see if it's as crazy as I remember it," said Frederick resident Dwight Heidel.

Heidel, who co-runs the Frederick Beer Review — a website that chronicles the city's beer scene — designed commemorative T-shirts and masks to mark the occasion. Each piece is printed with the image of a cicada and the words "Brew'd X."

In the first day since the merchandise has been available online, Heidel said he's received about 10 orders and a handful of encouraging comments.

"With COVID being what it was and everyone being all isolated and separated, it seemed like it could be a kind of fun social and social media thing to do," Heidel said. "It just seemed timely."

He's been talking to his young children about Brood X, he said, and is eager to show them just what the barrage of insects will be like.

Not everyone is looking forward to them, though. Although they don't pose any risk to people, animals or most plants, female cicadas carve v-shaped slits into tree branches in which to lay their eggs. In younger saplings, these cracks can cause branch breakage and death.

In a home garden setting, many people prevent that issue by putting netting up around their young trees, or waiting to plant them until later in the season. But for some farmers — like Robert Black, owner of Catoctin Mountain Orchard — netting just isn't practical.

"Boy, that's a cumbersome thing to do," Black said. "We've got hundreds of trees."

Instead, Black said, his team will monitor their trees and treat them with chemicals if any become particularly cicada-infested. There's no way to know how big a threat the bugs will pose until they arrive, he said.

"It's a wait-and-see guessing game to know what kind of pressure we're going to end up with," said Mark Shannon, a farm consultant who advises Black on pest control.

In some areas of Maryland — and all over the South — that waiting game is already over. According to Cicada Safari, a free app developed by researchers at Mount St. Joseph University that tracks Brood X's emergence, thousands of sightings have been recorded in the Washington, D.C., area. More than 700 have been reported in and around Baltimore. In the Frederick area, though, the app only shows 18 sightings.

The discrepancy is due to differences in soil temperature, Raupp said. The "cicada palooza," as he calls it, won't start in earnest until soil temperatures reach a consistent 64 degrees Fahrenheit. It's been held at bay by a handful of chilly nights, especially in the county's more mountainous regions.

While some patterns around periodical cicada's emergence are well-studied, many others remain something of a mystery even to entomologists, said Daniel Gruner.

Gruner, another entomology professor at the University of Maryland, said scientists still don't understand how, exactly, the cicadas manage to emerge like clockwork every 17 years.

Invertebrates definitely aren't known for their powerful brains, Gruner said, but some researchers think the cicadas mark time using a sort of internal molecular clock coupled with environmental cues from the soil warming and cooling around them.

"They may use that process — or something like it — to draw an 'X' on the wall, so to speak, to keep track of how many cycles have passed," he said. "That's the best hypothesis we have at this point."

Gruner wasn't at the university for the last periodical cicada invasion, he said. For 14 years, he's been waiting for the chance to speak to students, journalists and the public about the phenomenon.

"It's wonderful to have all these interested people," he said.

Raupp agreed. He's spent months urging the public not to fear the cicadas, he said, and to appreciate them instead.

"It's like having a BBC special in your own backyard," Raupp said. "It would just be a shame to miss it."

Follow Jillian Atelsek on Twitter: @jillian_atelsek